/// <summary>
/// Decrypt the data
/// </summary>
/// <param name="Data">The data to decrypt</param>l
/// <param name="Offset">The index where the data starts</param>
/// <param name="Length">The length to decrypt</param>
public void Decrypt(byte[] Data, int Offset, int Length)
{
lock (DecState)
{
int OrgLen = Length;
Length += Offset;
for (int round = 0; round < Rounds; round++)
{
using (PayloadWriter pw = new PayloadWriter(new System.IO.MemoryStream(Data)))
{
ulong temp_Value = DecState.IV[EncMode == WopEncMode.Simple ? 0 : DecState.IV_Pos]; //is being used for CBC Mode (Block-Cipher-Chaining Mode)
for (int i = Offset, k = 0; i < Length; k++)
{
pw.vStream.Position = i;
int usedsize = 0;
ulong value = 0;
ulong OrgReadValue = 0;
if (i + 8 < Length)
{
OrgReadValue = BitConverter.ToUInt64(Data, i);
usedsize = 8;
value = Decrypt_Core_Big(OrgReadValue ^ temp_Value, OrgLen, k);
pw.WriteULong(value);
}
else
{
OrgReadValue = Data[i];
usedsize = 1;
value = Decrypt_Core_Small((byte)OrgReadValue, OrgLen, k);
pw.WriteByte((byte)value);
}
temp_Value += OrgReadValue;
DecState.Seed += (int)value;
i += usedsize;
if (EncMode != WopEncMode.Simple)
{
DecState.Key_Pos += 1;
DecState.Salt_Pos += 1;
}
}
}
}
DecState.IV_Pos = (DecState.IV_Pos + 1) % DecState.IV.Length;
switch (EncMode)
{
case WopEncMode.GenerateNewAlgorithm:
{
InstructionInfo tempEncCode = null;
InstructionInfo tempDecCode = null;
FastRandom fastRand = new FastRandom(DecState.Seed);
for (int i = 0; i < DecState.Instructions.Length; i++)
{
GetNextRandomInstruction(fastRand, ref tempEncCode, ref tempDecCode);
DecState.Instructions[i] = tempDecCode;
}
if (UseDynamicCompiler)
{
DecState.Compile();
}
break;
}
case WopEncMode.ShuffleInstructions:
{
ShuffleInstructions(DecState.Instructions, DecState.Seed);
if (UseDynamicCompiler)
{
DecState.Compile();
}
break;
}
}
}
}